Aluminum alloys



Patented Oct. 31, 1933 UNITED STATES PATENT OFFICE Company of America, Pittsburgh, Pa., a corporation of Pennsylvania No Drawing. Application September 21, 1932 Serial No. 634,153

3 Claims.

The invention relates to aluminum base alloys containing magnesium and zinc and to such alloys of this general class as have superior casting properties.

The principal object of this invention is to provide an all-purpose casting alloy which may be used in either permanent mold or sand mold casting processes but which is particularly excellent as a material from which intricate castings may be made in permanent molds. Among the other objects of this invention is the, provision of an aluminum base alloy from which cast cooking utensils may advantageously be made.

The invention is predicated upon the addition of calcium to certain of the aluminum base alloys containing magnesium and zinc to produce new alloys of superior casting characteristics and such as are particularly useful in the casting of intricate or thin-sectioned shapes in permanent molds. The alloys to which we refer are those aluminum base alloys contaning 1.0 to 8.0 per cent by weight of magnesium, 0.5 to 6.0 per cent by weight of zinc, and 0.01 to 2.0 per cent by weight of calcium. These alloys, we have found, are characterized by high fluidity, by a marked absence of drossing during casting, and by good general casting properties such as ease of melting, handling, and pouring.

The alloys flow readily in the mold, filling thin sections with ease and facility. They do not burn or dross as do other alloys containing magnesium, and they produce sound, smooth-surfaced castmgs.

The castings produced by the use of these alloys are hard, of good strength and do not readily crack or fail in use. Moreover, they are capable of taking and retaining a high polish andv are particularly resistant to the pitting type of corrosion. For these reasons they are peculiarly adapted for use in the manufacture of cast cooking utensils, an application in which they have proved to be eminently suitable.

While particularly suited for these purposes, the alloys are likewise useful in the manufacture of many different types of castings, including those of thin section and intricate design, and thus have an all-purpose use which makes them very suitable as a common alloy in general foundry work.

When the alloys are used in the manufacture of castings in permanent molds, the amount of calcium is preferably about 0.1 to 0.4 per cent by weight of the total alloy. When the alloys are used in the manufacture of castings in sand molds, the best results are obtained with a calcium content of about 0.01 to 0.1 per cent by weight. Calcium may be present, however, in amounts of 0.01 to 2.0 per cent in either case without substantial impairment of the novel properties of the alloys. The amount of magnesium present may vary between about 1.0 to about 8.0 per cent by weight and the zinc present may vary from about 0.5 to 6.0 per cent by weight. The balance of the alloy is, in many cases, entirely aluminum. In other instances, however, other alloying elements, such as manganese, nickel, copper, silicon, etc., may be added to modify some property of the alloy or to introduce such new properties as hardness, strength and the like as these elements are known to impart to aluminum base alloys. We have determined, however, that best results are obtained with the alloys containing at least about 80 per cent by weight of aluminum, and the term aluminum base is used in the appended claims to denote an alloy of an aluminum content of 80 per cent or more. The aluminum used in preparing the alloys may be pure or it may contain usual impurities, such as iron. Iron in itself is not a detrimental impurity in these alloys, for some purposes, in amounts as high as 2.0 per cent and may even be deliberately added. Usually, however, it is preferable to use a good grade of virgin aluminum ingot for the best results.

The alloys may be compounded by first melting the aluminum and then adding to the melt the proper amount of magnesium, zinc, and calcium.

No particular order of addition is necessary, however, and other methods of making the alloys may be successfully used. Among the specific alloys which have given excellent results in tests and services, an alloy containing 3;75 per cent by weight of magnesium, 2.0 per cent by weight of zinc, and 0.2 per cent by weight of calcium may be mentioned as possessing particularly excellent properties.

Having thus described our invention, we claim:

1. A metallic alloy consisting of 1.0 to 8.0 per cent by weight of magnesium, 0.5 to 6.0 per cent by weight of zinc, and 0.1 to 2.0 per cent by weight of calcium, the balance being substantially aluminum.

2. A metallic alloy consisting of 1.0 to 8.0 per cent by weight of magnesium, 0.5 to 6.0 per cent by weight of zinc, r nd 0.1 to 0.4 per cent by weight of calcium, the balance being substantially aluminum.

3. A metallic alloy consisting of 3.75 per cent by weight of magnesium, 2.0 per cent by weight of zinc, and 0.2 per cent by weight of calcium, the balance being substantially aluminum.

ROBERT T. WOOD. OTTO H. HEIL. 

